JP3152757B2 - Pulse tube refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse tube refrigerator, and more particularly to a pulse tube refrigerator capable of improving efficiency.

[0002]

2. Description of the Related Art Conventionally, a pulse tube refrigerator is known as a refrigerator having a relatively simple structure and a relatively low temperature. There are various types of this pulse tube refrigerator. Each of them basically has a cold generator in which a regenerator and a pulse tube are connected in series, and guides a high-pressure refrigerant gas through the regenerator to the inside of the pulse tube and then discharges and expands it in the reverse path. Thereby, cold is generated in the pulse tube.

In order to increase the amount of cold generated in such a pulse tube refrigerator, it is necessary to provide a phase difference between the phase of the pressure fluctuation in the pulse tube and the phase of the displacement of the refrigerant gas. There is. For this reason, many conventional pulse tube refrigerators have a system for providing a phase difference. FIG. 7 shows a conventional pulse tube refrigerator provided with a system for providing a phase difference. That is, in the figure, 1 indicates a cold generator, and 2 indicates a gas compressor.

The cold generator 1 includes a regenerator 3 and a pulse tube 5 connected in series to the regenerator 3 via a low-temperature heat exchanger 4. The regenerator 3 contains a regenerator 7 made of stainless steel or copper mesh in a container 6 made of a heat insulating material or a metal material having a low thermal conductivity. The pulse tube 5
It is formed in a pipe shape from a heat insulating material or a metal material having low thermal conductivity.

[0005] The inlet 8 of the regenerator 3 is connected to the gas compressor 2. The gas compressor 2 comprises a cylinder 9 and a piston 1
This is a reciprocating type that includes a compression chamber 11 composed of “0” and “0”. One end of a piston rod 12 is connected to the back of the piston 9, and the other end of the piston rod 12 is guided by a guide mechanism 13 and connected to a reciprocating drive source (not shown).

On the other hand, between the end of the pulse tube 5 and the inlet 8 of the regenerator 3, there is provided a so-called double inlet passage pipe 14 through which the refrigerant gas flows. Is provided with a valve 15 for adjusting the flow rate. The end of the pulse tube 5 also communicates with a buffer tank 17 via an orifice valve 16. A refrigerant gas such as helium gas is sealed at a predetermined pressure in the system connected as described above.

In the pulse tube refrigerator configured as described above, when the piston 10 moves upward in the figure and the volume in the compression chamber 11 decreases, the compressed refrigerant gas is discharged.
On the one hand, it flows into the pulse tube 5 through the regenerator 3, and on the other hand, it flows into the pulse tube 5 and the buffer tank 17 via the pipe 14.
When the piston 10 moves backward in the figure, the refrigerant gas in the pulse tube 5 is discharged to the regenerator 3 on the one hand.
It flows into the compression chamber 11 through the inside, and on the other hand, flows into the compression chamber 11 via the pipe 14.

[0008] With such a flow of the refrigerant gas, a pressure fluctuation occurs in the pulse tube 5, causing cold. A part of the cold cools the object to be cooled via the low-temperature heat exchanger 4. The remainder is used for cooling the cold storage material 7 when the refrigerant gas returns in the reverse route.

At this time, an optimal operating condition can be created by adjusting the opening of the valve 15 and the orifice valve 16. That is, the pipe 14, the valve 15, the orifice valve 16, and the buffer tank 1
7 contributes to the formation of the above-mentioned phase difference.

However, in the conventional pulse tube refrigerator configured as described above, since the above-described adjustment range of the phase difference is limited by the gas compressor 2, it is necessary to sufficiently increase the phase difference. For example, there is a problem that the efficiency is lower than that of a Stirling refrigerator in which an expansion piston is provided in a low-temperature portion and a phase difference is forcibly provided by the piston. Also, the compression efficiency is reduced due to the sliding resistance between the cylinder 9 and the piston 10,
This also reduced the efficiency of the refrigerator.

[0011]

As described above, the conventional pulse tube refrigerator has the advantage of not requiring a movable part in the low temperature part, but has a problem of low efficiency. Accordingly, an object of the present invention is to provide a pulse tube refrigerator capable of improving the refrigeration efficiency without impairing the above-mentioned advantages.

[0012]

[Means for Solving the Problems] In order to achieve the above purpose
A cold generator having at least a regenerator and a pulse tube connected in series, a gas compressor, and a buffer tank connected to an end of the pulse tube, and a refrigerant compressed by the gas compressor. An orifice configured to introduce gas into the pulse tube through the regenerator and then to suck the gas into the gas compressor in a reverse path, and to connect an end of the pulse tube directly to the end;
Connected to the buffer tank via a valve.

[0013]

[Function] Piping volume between pulse tube and orifice valve
Since the product can be eliminated, the phase difference between the phase of the pressure fluctuation in the pulse tube and the phase of the cooling gas displacement can be increased, and as a result, the efficiency can be improved.

[0014]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a pulse tube refrigerator according to one embodiment of the present invention. In this figure, the same elements as those of FIG. 7 are denoted by the same reference numerals. Therefore, a detailed description of the overlapping part will be omitted.

The pulse tube refrigerator according to this embodiment is different from the conventional refrigerator in that a porous plug 20 having an appropriate fine ventilation path is interposed between the end of the pulse tube 5 and the buffer tank 17. It is in.

With this configuration, the refrigeration principle itself is the same as that of the conventional refrigerator. However, by providing the porous plug 20 instead of the orifice valve, the phase of the pressure fluctuation in the pulse tube 5 and the refrigerant gas The phase difference between the displacement and the phase can be increased, and the efficiency can be improved.

FIG. 2 shows the pulse tube refrigerator according to the embodiment and the conventional pulse tube refrigerator shown in FIG.
The refrigeration capacity characteristics at K are shown. The refrigerator used in the experiment is as follows. The gas compressor 2 has an inner diameter of 60 mm and a stroke of 15 to 30 mm. The regenerator 3 has an axial length of 100 mm and two types of inner diameters of 34 mm and 28 mm. Is 1000cc.

In FIG. 1, the horizontal axis represents the operating frequency. In the figure, the broken line indicates the characteristics of the conventional refrigerator, and the solid line indicates the characteristics of the refrigerator according to the present embodiment. In the refrigerator according to the present embodiment, since the amount of cold generated can be increased, the refrigerator exhibits higher refrigerating capacity characteristics than the conventional refrigerator.

Although some refrigerators do not have the double inlet pipe 14, the use of the porous plug 20 is also effective in such a refrigerator.

FIG. 3 shows a pulse tube refrigerator according to another embodiment of the present invention. In this figure, the same elements as those in FIG. 1 are indicated by the same reference numerals. Therefore,
A detailed description of the overlapping part will be omitted.

The difference between this pulse tube refrigerator and the above embodiment is that the end of the pulse tube 5 is connected to the buffer tank 17 via an orifice valve 21 connected directly to this end, and the end of the pulse tube 5 is connected to the end of the pulse tube. Is connected to the pipe 14 for the double inlet via the control valve 22 directly connected to the second valve.

With such a configuration, the refrigeration principle itself is the same as that of the conventional refrigerator, but the piping volume between the pulse tube 5 and the orifice valve 21 and the piping between the pulse tube 5 and the control valve 22 are set. Since the volumes can be eliminated, the phase difference between the phase of the pressure fluctuation in the pulse tube 5 and the phase of the displacement of the refrigerant gas can be increased, and the efficiency can be improved. . In addition, piping 14 for double inlet
For those that do not have the above, the effect can be expected by providing the orifice valve 21 in the above relationship.

FIG. 4 shows a pulse tube refrigerator according to another embodiment of the present invention. Also in this figure, FIG.
The same elements as those of FIG. 7 are indicated by the same reference numerals.
Therefore, a detailed description of the overlapping part will be omitted. This pulse tube refrigerator differs from the previous embodiment in the configuration of the gas compressor 2a and the gas flow system.

The gas compressor 2a is of a reciprocating type having a compression chamber 33 composed of a cylinder 31 and a piston 32. The bottom wall of the cylinder 31 is closed, and the piston rod 34 penetrates the bottom wall in an airtight and slidable manner and is connected to a driving device (not shown), for example, a voice coil motor type. And compression chamber 3
3 is connected to the inlet 8 of the regenerator 3, and a back chamber 35 formed on the opposite side of the compression chamber 33 from the piston 32 is connected to a buffer tank via a pipe 36 and a valve 43 for adjusting the flow rate. It leads to 17.

The peripheral wall of the cylinder 31 is formed in a double structure, and the inner wall 37 is formed of ceramic. An annular groove is formed on the outer peripheral surface of the piston 32, and a seal ring 38 for sealing between the cylinder 31 and the piston 32 is mounted in the annular groove. The seal ring 38 is weakly pressed against the inner wall 37 by the force of a spring 39 mounted in the annular groove. Further, a flange 40 is provided at a portion protruding outside the piston rod 34, and a coil spring 42 for supporting a movable portion including the piston 32 is mounted between the flange 40 and the stationary member 41. ing. The spring constant of the coil spring 42 is set to a value smaller than the gas spring constant of the refrigerant gas acting on the piston 32.

With such a configuration, when the piston 32 moves upward in the figure and the volume in the compression chamber 33 is reduced, the compressed refrigerant gas and the regenerator 3
It flows into the pulse tube 5 through the inside, and on the other hand, flows into the pulse tube 5 and the buffer tank 17 via the pipe 14. At this time, a part of the refrigerant gas in the buffer tank 17 flows into the rear chamber 35 via the pipe 36. When the piston 32 moves downward in the drawing, the refrigerant gas in the pulse tube 5 flows into the compression chamber 33 through the regenerator 3 on the one hand, and into the compression chamber via the pipe 14 on the other hand. It flows into 33. At this time, the refrigerant gas in the rear chamber 35 is
Flows into the buffer tank 17 through the pipe, and the refrigerant gas in the buffer tank 17 flows through the pipe 14 and the pulse tube 5.
Flows inside. A pressure fluctuation occurs in the pulse tube 5 with the flow of the refrigerant gas, and cold occurs.

In this case, since the movable portion including the piston 32 is supported by the coil spring 42 having a smaller spring constant than the gas spring constant of the refrigerant gas acting on the piston 32, the piston 32 tilts. There is no such thing. Therefore, since the seal ring 38 does not hit one side, the cylinder 31 and the piston 32
Not only can be reliably sealed, but also the sliding resistance can be reduced, and as a result, the efficiency as a refrigerator can be improved. Further, with this configuration, the resonance frequency of the piston 32 can be adjusted to a frequency band with a high refrigeration efficiency by adjusting the weight of the piston 32. Therefore, the refrigeration efficiency can be further improved. FIG. 5 shows an example of use of a pulse tube refrigerator.

Here, an example in which the inner tank of the heat insulating container is cooled by a pulse tube refrigerator is shown. That is, in the figure, 51 indicates the inner tank of the heat insulating container, 52 indicates the outer tank, and 5
Reference numeral 3 denotes a vacuum heat insulating layer formed between the inner tank 51 and the outer tank 52.

In the vacuum heat insulating layer 53, the one-stage regenerator 3a,
The low-temperature heat exchange section 4a and the first-stage pulse tube 5a are connected in series. Further, the low-temperature heat exchange section 4a is a two-stage regenerator 3
b, connected to the second-stage pulse tube 5b via a low-temperature heat exchange section 4b thermally connected to the inner tank 51. In this example, the two-stage pulse tube 5b has an axial length of 1
It is set to be at least twice as large as that of the step pulse tube 5a. An intermediate position in the axial direction on the outer peripheral surface of the second-stage pulse tube 5b and the low-temperature heat exchange section 4a are connected by a heat conductor 54. The inlet of the one-stage regenerator 3a is connected to the gas compressor 2 via a pipe 55 provided to penetrate the outer tank 52 airtightly. Similarly, the end of the first-stage pulse tube 5a and the end of the second-stage pulse tube 5b are respectively connected to the buffer tanks 17a and 17a via pipes 56 and 57 and orifice valves 16a and 16b provided through the outer tank 52 in an airtight manner. 17b.

With such an arrangement, the low-temperature heat exchange section 4
The temperature of the low-temperature heat exchange section 4b is lower than a, and the inner tank 51 is cooled at this low temperature. In this case, since the two orifice valves 16a and 16b and the two buffer tanks 17a and 17b can be exposed, adjustment and maintenance can be facilitated.
Also in the pulse tube refrigerator arranged in this manner, the refrigeration efficiency can be improved by employing the method described in each of the embodiments. FIG. 6 shows another example of use of the pulse tube refrigerator.

Generally, in a heat insulating container provided with a vacuum heat insulating layer, a heat shield plate is provided in the vacuum heat insulating layer to prevent heat from entering by radiation, and the heat shield plate is cooled to a predetermined temperature. I have. In the example shown in FIG. 6, the cooling of the heat shield plate and the support of the heat shield plate are performed by a pulse tube refrigerator. That is, in the figure, 61 indicates the inner tank of the heat insulating container, 62 indicates the outer tank, 63 indicates the vacuum heat insulating layer formed between the inner tank 61 and the outer tank 62, and 64 indicates the inside of the vacuum heat insulating layer 63. 2 shows a heat shield plate arranged so as to surround the inner tank 61.

The regenerator 3 and the pulse tube 5 of the pulse tube refrigerator are disposed between the outer tub 62 and the heat shield plate 63 so as to also serve as a support for supporting the heat shield plate 64 with respect to the outer tub 62. Further, the low-temperature heat exchanging section 4 is a heat shield plate 64.
Is thermally connected to In the drawing, reference numeral 65 denotes a cryogenic liquid such as liquid helium, and 66 denotes a heat insulating support.

In this example, the pulse tube refrigerator is provided only at one place. However, all or a plurality of the heat insulating support members 66 supporting the heat shield plate 64 may be replaced with the pulse tube refrigerator. Good.

The present invention is not limited to the embodiment described above. That is, in each of the above-described embodiments, the entire cold storage unit is filled with the cold storage material having the same composition.For example, when a stainless steel mesh and a copper mesh are used as the cold storage material, the stainless steel mesh is used. Efficiency can be improved by filling the high-temperature side of the regenerator with a copper mesh on the low-temperature side of the regenerator. That is,
What has a large specific heat should just be filled on the low temperature side. Further, in a pulse tube refrigerator other than that shown in FIG. 4, a gas compressor other than a reciprocating gas compressor may be used. In this case, needless to say, a valve for switching between discharge and suction is required.

[0036]

As described above, according to the present invention,
A highly efficient pulse tube refrigerator can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a pulse tube refrigerator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a refrigerating capacity characteristic of the refrigerator at 80K in comparison with that of a conventional refrigerator;

FIG. 3 is a schematic configuration diagram of a pulse tube refrigerator according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a pulse tube refrigerator according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining an example of use of a pulse tube refrigerator.

FIG. 6 is a schematic view for explaining another example of use of the pulse tube refrigerator.

FIG. 7 is a schematic configuration diagram of a conventional pulse tube refrigerator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cold generator 2, 2a ... Gas compressor 3 ... Regenerator 4 ... Low temperature heat exchanger 5 ... Pulse tube 14 ... Piping 15 ... Control valve 16 ... Orifice valve 17 ... Buffer tank 20 ... Porous plug 21 ... Orifice valve 22 ... Control valve 31 ... Cylinder 32 ... Piston 33 ... Compression chamber 34 ... Piston rod 35 ... Back chamber 36 ... Piping 37 ... Inner wall 38 ... Seal ring 39 ... Spring 42 ... Coil spring

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Matsubara 2-3-3 Oanakita, Funabashi City, Chiba Prefecture (56) References JP-A-4-225755 (JP, A) JP-A-4-165269 (JP, A) JP-A-2-298764 (JP, A) JP-A-4-268168 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 9/00 311

Claims (2)

(57) [Claims] 1. A cold generator comprising at least a regenerator and a pulse tube connected in series, a gas compressor, and a buffer tank connected to an end portion of the pulse tube, wherein the compressor is compressed by the gas compressor. In the pulse tube refrigerator configured to introduce the refrigerant gas into the pulse tube through the regenerator and then into the pulse compressor through a reverse path, the terminal end of the pulse tube is A pulse tube refrigerator connected to the buffer tank via an orifice valve directly connected to the terminal portion. 2. The method according to claim 1, wherein the inlet of the regenerator and the end of the pulse tube are connected by a double inlet passage having a control valve directly connected to the end. Pulse tube refrigerator.